Most dry shipper enquiries arrive as a specification question. Which size, which hold time, which model. The prior question, and the more useful one, is whether you should own one at all, because a vessel used four times a year and a vessel used four times a month are different commercial decisions entirely.

Construction and Classification: Why the Paperwork Follows the Design

A dry shipper holds liquid nitrogen absorbed into a porous inner matrix rather than as free liquid. Samples travel in the vapour phase, the vessel can be inverted without spilling, and there is no free liquid available to escape.

That construction is precisely why the shipper itself travels as not restricted under Special Provision A152 of the IATA Dangerous Goods Regulations, provided the packaging cannot build pressure or release nitrogen in any orientation and the air waybill carries the words not restricted together with the special provision number.

Packing Instruction 650 of the same regulations governs the biological samples inside, where those are classified as UN 3373 Category B. It applies to the samples, not to the nitrogen holding them cold.

Those two provisions are constantly conflated, including across a good deal of supplier literature. A dry shipper is not exempt from Packing Instruction 650. Packing Instruction 650 was never about the nitrogen.

The Case for Hiring

Infrequent shipments make the strongest case. A purchased shipper used a few times a year spends most of its life empty in a corner, and an empty shipper still requires storage space, periodic inspection and charging before use.

Unusual sizes make a second. A one off shipment needing more capacity than your own unit holds is a hire, not a justification for buying a second vessel that will then join the first in the corner.

Capital constraints make a third, and it is more practical than it sounds. Hire moves the cost out of capital expenditure and into the shipment, which is usually easier to approve and considerably easier to recharge to whoever the shipment is for.

Peak cover makes the fourth. A unit with a regular pattern and occasional surges is better served hiring for the surge than owning for the peak.

The Case for Owning

Frequency is the obvious argument, and the crossover point sits lower than most people expect once staff handling time is counted properly.

Control is the stronger one. With your own vessel you know its history, whether it has been dropped, and how it performed on the last shipment. With a hired unit you are relying entirely on somebody else’s inspection regime, and a dry shipper that has taken a knock can carry a degrading vacuum with no external sign whatsoever.

Readiness is the third. Charging is not instant, so owning a unit means preparing on your own timetable rather than a hire company’s, which matters when a transfer date moves.

Hold Time: The Figure Most Often Misread

Published hold times are measured under favourable and clearly defined conditions: upright, unopened, at moderate ambient temperature.

Real shipments meet none of those conditions reliably. Orientation changes in transit, ambient temperature varies considerably, customs holds happen without warning, and every opening costs hold time that is not recoverable. The published figure should be read as an upper bound under ideal conditions, with margin built for the delay you have not planned for rather than the journey you have.

Where a supplier quotes a hold time without stating the conditions under which it was measured, that figure is not usable for planning. We will not quote one that way.

Charging: Where Shipments Actually Fail

An undercharged shipper is the most common cause of a failed cryogenic transport, and it is entirely preventable.

The absorbent matrix has to be fully saturated, which takes appreciably longer than most protocols allow, and the vessel must then be inverted and drained so that no free liquid remains. Skipping the drain leaves free nitrogen in the vessel, which changes both its regulatory position and its behaviour in transit.

Weigh the unit before and after charging and record both figures. Weight is the only practical measure of how much cold mass is genuinely in the vessel, and it is the only check that will catch a matrix that has not taken a full charge.

BCGA Code of Practice 30, the safe use of liquid nitrogen dewars, records that asphyxia due to oxygen deficiency is often rapid with no prior warning to the victim. That is the reason a freshly charged shipper does not share a lift with a person. Send it up and take the stairs.

Sizing Across the Range

The CryoStork range runs from the V2 at 2 litres, through the V3, V4 and V6, to the V10 at 10 litres. Sizing follows the number and format of samples together with the journey length, rather than the largest unit the budget will absorb, because a larger shipper is heavier for staff to handle and more expensive to ship.

Whether hire or purchase is right for you depends almost entirely on shipment frequency and how much control you need over the vessel’s condition. If you tell us the route, the sample format and how often you expect to ship, we can tell you which of the two makes commercial sense and which capacity fits. Speak to Cryolab.